Obstructive sleep apnea (OSA) is a major medical problem that affects 18-20 million people in the United States. Patients with OSA suffer from fragmented sleep, chronic fatigue, daytime sleepiness, lack of concentration and memory problems with consequences including increased risk of motor vehicle accidents and the development of cardiovascular diseases with risk for sudden death. The current gold standard diagnostic modality, overnight polysomnography is inconvenient, unable to provide information on upper airway structure and anatomy, and cannot identify the obstruction sites of upper airway in OSA patients which is important in choosing the appropriate treatment, especially surgical intervention. The long-term research goal of this project is to develop a modality to provide additional anatomic information as a valuable complimentary study to conventional sleep studies for (1) real time volumetric airway anatomy imaging during sleep and while awake; (2) physiological investigation of OSA; and (3) identification of obstruction sites that aids in choosing the most appropriate treatment for potential surgical candidates. The project proposes development and testing of an innovative high speed long range endoscopic Fourier domain optical coherence tomography (FDOCT) system capable of non-invasive real time acquisition of quantitative anatomic information such as cross sectional area and shape of upper airway for the characterization of OSA. The developed system will be tested and optimized with phantom models and ex vivo animal imaging. Then, in pilot clinical studies, FDOCT scanning will be performed in subjects with obstructive apneas, compared and correlated with standard overnight polysomnography. The proposed research training program will provide excellent experience and mentoring in the methods and conduct of biomedical and clinical research that will complement the candidate's existing expertise in engineering and optics. A team of mentors who are recognized experts and leaders in airway physiology, sleep medicine and biomedical imaging have been assembled for this K25 program. Co-mentor Dr. Zhongping Chen, professor of Beckman Laser Institute and biomedical engineering at University of California Irvine has an established track record in the development of optical imaging methods and translational research. Co-mentor Dr. Matthew Brenner, Professor and Chief of Pulmonary Medicine at the Lung Center at the University of California Irvine has experienced similar success in the study of development of new laser diagnostic technologies for translation to clinical pulmonary and critical care medicine. Co-mentor Dr. Catherine Sassoon, Chief of Division of Pulmonary & Critical Care in VA Long Beach Healthcare System and Professor of Medicine in Residence, UC Irvine, is board certified in Sleep Medicine, Pulmonary, Internal Medicine and Critical Care with over 30 years of experience in respiratory physiology. She has serves as a member of Editorial Board of American Journal of Respiratory and Critical Care Medicine and Editorial Board of Respiratory Care. Co-mentor Michael Dickel, Ph.D., Staff of Sleep Disorders Laboratory in VA Long Beach Medical Center, is a board-certified sleep medicine specialist with extensive experience in Sleep Medicine, sleep physiology, sleep research, Statistics and training Pulmonary Fellows. The opportunities of this career award will provide the candidate valuable mentorship, training, and resources to further develop his research skills and expand his knowledge and experience in the conduct of experimentation both in the laboratory and in the clinic under the close supervision, leading to advancement to independent researcher level by completion of this proposed project.